Growth Performance of Alfalfa(Medicago sativa)under Different Nitrogen Application Levels

不同氮素添加水平对紫花苜蓿生长性能的影响（英文）

Nitrogen addition is rather important to the growth of alfalfa. In this study, the effects of different nitrogen application levels on various growth characteristics of alfalfa were investigated. The results showed that nitrogen application exhibited no significant effects on plant height and stem diameter but posed significant effects on branch number of alfalfa. Branch number of alfalfa in each cutting raised with the increasing application level of nitrogen, with significant differences among different treatments （P〈0.05）; individual aboveground biomass increased with the increasing application level of nitrogen, but the increasing trend gradually tended to be steady from the first to the fourth cutting. Nitrogen application affected significantly （P〈0.05） individual aboveground biomass of alfalfa in the first, second and fourth cutting, but exhibited no significant effects on individual aboveground biomass of alfalfa in the third cutting. With the increase of nitrogen application level, total surface area, total volume, collar diameter and crossing number of alfalfa roots increased gradually, but total length, average diameter and furcating number of alfalfa roots increased first and then declined. Total length, average diameter and furcating number of alfalfa roots reached the maximum in N60 treatment.

氮素添加对于紫花苜蓿生长具有重要作用。该试验研究了不同氮素添加水平对于紫花苜蓿生长性能各个指标的影响机制。结果表明,施氮对不同茬次苜蓿的株高、茎粗影响效果不明显,而对苜蓿的分枝数影响效果显著。每一茬次的苜蓿分枝数都随施氮量的增加而增加,并且处理之间差异显著(P<0.05);苜蓿单株地上生物量随施氮量的增加而增加,但从第一茬到第四茬,增加的趋势逐渐平缓。施氮对第一茬、第二茬和第四茬的苜蓿单株生物量有显著影响(P<0.05),而对第三茬苜蓿单株生物量影响不显著;随着施氮量的增加,紫花苜蓿根系的总表面积、总体积、根颈粗和交叉数呈逐渐增加的趋势,而紫花苜蓿的总根长、平均直径和分叉数随施氮量的增加并未呈现逐渐增加的趋势,而是先增加后降低,N60处理的紫花苜蓿总根长、平均直径和分叉数最大。